Spray dried soap and process of making same



Patented July 7, 1936 UNITED STATESPATENT' oFFicE srau' n 82 2: raoonss or Carleton Ellis, Montclair, N. 1., assigncr to Procter .& Gamble Company, .11..

a corporation oi. Ohio The hi0,

s (on. 87-16) This invention relates to soap in a comminuted state obtained by spray drying soap having a substantial degree of hydration.

It has been proposed to spray dry soap solutions of a dilute character, or what would be generally called soap in the nigre form, and also to spray dry soap in the concentrated neat form, termed kettle soap. The dilute solution form of soap may range from stock containing 90% or more water, to possibly evenas low as 60% of water. The kettle soap ordinarily contains about 30% of water, although at times it may be made with a somewhat higher proportion. r

i The spray drying of the dilute solutions of soap involves expenditure of inordinate amounts of fuel to eliminate the high proportion of water present. The product obtained from the employment of such dilute solution also tends to 0 be atrifie too small in particle form, and too fragile to be of great commercial utility.

On the other hand the spray drying of neat, or kettle soap, with its component of approximately 30% of water may not permit so close 5 an adjustment of drying conditions in ordinarycommercial practice that a definite and controlled content oi. moisture appears in the resulting product.

Between the dilute solution of soap, or nigre 0 type soap, and neat soap, or kettle type soap, there'exists a zone commonly termed 'middle soap, which is aproduct of a peculiar condition of hydration forming stifl gummy masses, normally of far too high consistency to be usable F5 in spray dry apparatus. See the article "Middle soap by Ferguson 8: Richardson in Industrial & Engineering Chemistry, 1932', page 1329.

It should be understood in spray drying that nozzle apertures of very small diameters cuslo tomarily are employed in order that resulting spray may be free from coarse particles. While, therefore, it is possible to spray dry dilute solutions of soap, as this is in a readily flowable condition, and likewise to spray-dry the more concentrated kettle soap, the extraordinary viscous gummy qualities of middle soap have heretofore precluded its use in the production of spray-dried detergents.

However, middle soap, (which is iii-what is termed the nematic state) contains water in combination with the soap molecules in the form of chemical water of hydration and the spray drying of a stock of this character permits the retention of the peculiarly-combined water characteristic, of middle soap to yield a spray dried product having an adequate moisture content. This residual water seems to aid in conferring on the product an excellent degree 01 solubility when used as a detergent.

The spray drying operation as commonly 5 practiced, with the use,'for example, 01. the apparatus shownin the Lamont Patent 1,652,900

, seemingly is not conducive to close and deflnite control of moisture content. A dilute S01: tion of soap when sprayed thus, due to the size 10 of the drop formation, or to absence of a definitecondition of water of hydration, usually gives too dry a product, and also is inclined to be light, voluminous and dusty.

A product, which, when shaken out of a package for use as a detergent, forms a cloud 0! dust is objectionable and I seek in accordance with the present invention toobtain a particle formation of suilicient size, which is readily soluble and which avoids any objectionable 2o formation of dust in use.

Although neat soap may be spray dried to a product having suitable particle formation, which is fairly uniform and generally free from dust, there is no opportunity in view of the small amount of water present in the neat, or kettle stock, to provide suilicient latitude in the spray drying step for retention of adequate moisture.

Middle soap, however, contains hydrated soap 80 particles in a condition fully adequate for spray drying to obtain particles with a desired higher moisture content without the necessity of subsequent h'umidiflcation, and the like.

As indicated, middle soap in its viscid gummy state is of too high a degree of consistency to. pass through spraynozzles, but it is possible, in. accordance with the present invention to convert the middle soap into a more fluent, or liquid form, by incorporation of a degumming agent; 40 In this way a stock may be secured for spraying purposes which is entirely suitable in consistency, and may be spray dried to yield a product containing if desired, 10% and upward of water preferably a water content between the range 5 of 10 and 20%. Despite this water content the material feels dry to the touch, and is free from any objectionable proportion of dust, while still being adequately soluble for household, orother purposes involving the use of soap.

A definite type of particle formation results from spray drying degummed middle soap; the

' usual appearance of the particle being that of a glassy, hollow ovule, or globule, the walls of which are not thin and fragile, such as result 55 from the spray drying of dilute solutions of soap.

Furthermore, the relatively heavy wall structure water in the free state in the middle soap could way of illustration.

expand almost instantly when the sprayed parti cles enter the hot spray chamber giving the customary hollow spherical form characterizing spray dried products of various kinds other than those formed from soap. The chemically combined water in the soap is not, however, liberated as quickly, and as the formed particle travels throughthe drying chamber becoming hotter as a result of such exposure, a temperature seems finally to be reached where chemical water is given off creating the wall vesiculations and yielding what ordinarily appears to be a glassy particle of generally ovoid or globular form having walls carrying small secondary bubbles, or vesiculations.

It has been supposed that a glass-like particle would not have the same meritorious degree of solubility as the more opaque particle of spongious wall obtained by the spray drying of neat soap. But, by the employment of middle soap, carrying soap material in a chemically hydrated state a quasi-glassy wall structure may be obtained so thoroughly vesiculated as to achieve extremely rapid solubility.

The advantages of a soap particle in the form obtained by this invention are, among others, a high degree of particle rigidity and strength ascribed to origin from the presence of initial water corresponding to the middle phase} a good degree of solubility ascribed to a notable condition of wall vesiculation; and a particle size adequate to confer freedom of flow of the dried material from its container and also a comparative freedomfrom dust.

Despite its vesiculations the wall strength is adequate to give that degree of stability which provides a self sustaining particle, not readily fracturing in handling.

The middle soap stock, employed in accordance with the present invention, and containing a degumming agent or component, may be prepared in different ways. A middle soap in a thick gummy condition may be produced by adding adequate water to neat soap, or any other concentrated soap material, and this gummy stock may be beaten up by means of powerful mixers with the degumming agent, which preferably may be introduced substantially free from water in order not to upset in an objectionable way the degree of chemical hydration desired in the stock employed in the present process.

Another way to obtain the middle soap is to evaporate water from dilute soap until the needed condition results. This, however, is a more costly method, -and is only mentioned by On the other hand the degumming or fiuxing agent in aqueous solution may be added to a soap stock which is in the neat range, the proportion of water in. such solution being sufilcient the following:

if no .degumming agent is present to cause a decided thickening due to formation of normal gummy middle soap. Or part of the water may be added in the degumming solution and the remainder in' any other suitable manner. The 5 batch is thoroughly agitated.

The product so made will befound no longer. extremely viscid and non-flowable, but will be adequately liquid for spray drying, especially when the stock is first heated and then pro- 10 pelled under pressure into the spray drying chamber. This method of operation is preferably employed in carrying out the present process.

Among the degumming agents are included 15 various alkaline salts such as; sodium carbonate, sodium bicarbonate, sodium acetate, sodium borate, or .borax, tri-sodiumphosphate, sodium silicate, or water glass, also now-alkaline salts such as; sodium chloride, sodium sulphate, and 20 the like. The employment of saponifled rosin in minor proportion, likewise is not precluded. Most of the salts mentioned may be obtained sufficiently free from moisture so that their addition in requisite quantities to the middle 25 soap will not upset a desired condition of chemical hydration. Sodium silicate, however, is usually obtainable in the form of a solution which may carry perhaps 40% of silicate to 60% of water. The addition of sodium silicate solution 30 to the middle soap, or its incorporation with stock destined to be brought in the middle soap range should be such that due allowance is made i for the added water, in order as stated, to avoid destruction of the chemically combined water of 35 hydration, conferring vesiculations within the wall structure, as previously pointed out.

Examples of compositions which may be used for purposes of illustration of this invention are Kettle (neat) soap was made in the usual way by saponifying fats with caustic soda. The fats used were 20, parts by weight of cocoanut oil to parts of tallow. Water was added to give a total water content of about 50% yielding a middle soap as a gummy mass.

Example 1.To middle soap, as above, there was added 1% by weight of common-salt (NaCl). In this example and following the proportions are by weight and the percentage of the degumming agent is based on the total (not dry) weight of the middle soap. The salt was worked into the middle soap and on heating in a closed receptacle for a short time the gummy nonfiowing. properties of the middle .soap disappeared yielding a clearheavy bodied syrupy iggay-stock material which flowed freely at Example 2.-Like Example 1, but with 3% of salt. At F. flows more as a magma or emulsion. i

Example 3.--Like Example 1, but with 5% of salt: In a precipitated condition flowing as a magma at 185 F.

Example 4.-Sodium sulphate used, behaved 65 in a manner similar to sodium chloride.

Example 5.--Trisodium phosphate in the proportion of 2% was used in place of sodium chloride. At 185' F. a free-flowing syrup resulted, not quite as clear as that obtained by Example 1. Y

Example 6.A very liquid fluent syrup resulted at 185 F. on incorporating in the middle soap.2% of trisodium phosphate and 2% of soda ash (anhydrous sodium carbonate).

phate of Example 5 from 2% to 5% increased the consistency (at 185 F.) and reduced the flow.

Example 8.--10% of trisodium phosphate gave a still less fluent product of relatively slow flow. Example 9.A fair flow was obtained by incorporating the middle soap material with 2% of soda ash and 2% of sodium silicate solution (containing about 60% water). I

Middle soap alone made as above when kept at 185 F. in a tight receptacle did not soften to a flowable condition.

In spraying the degummed middle soap care should be taken not to increase flowability to an extent "such that very small fine particles make up the bulk of the finished spray-dried product and cause objectionable dust to arise when handling. By lowering the temperature of the degummed middle soap which may be too fluent at 185 F. to a lower point such as 170 F. or 140 F., and the like, a regulation of particle size is promoted. Thus there are several waysof regulating particle size.

(a) Temperature control.

(b) Soap pressure control.

() Proportion of degumming agent.

((1) In some cases adjustment of spray nozzles or change from a pressure type to air atomiza-' tion is helpful.

Example 10.Using the same middle soap stock introduce up to 1 of caustic soda.

When the degumming'. agent is added in such proportion that the composition (maintained by heat in a flowable condition) tends ultimately to show considerable precipitatiomthe composition preferably is spray-dried prior to the beginning of precipitation. Since the latter change takes place slowly there is afforded in most cases sufiicient time to spray-dry the dispersion. The invention also contemplates the spray-drying of flowable dispersions which if allowed to stand in their initial state in a heated atmosphere would coagulate or precipitate to form slurries.

Preferably, however, I use a relatively low proportion of the degumming agent ranging in most cases from less than 1% to 2 or 3%.

When rosin is present in considerable proportion, the relative quantity of the degumming.

agent may be decreased, if desired, in any suitable proportion but preferably in the ratio of' reduction (when the degumming agent is present in an amount above three percent and upwards to ten percent or higher) of about one percent for each five percent of rosin soap present.

It should, however, be borne in mind that rosin impairs the color of thedried soap and, if present in high proportion, tends to induce an undesirable degree 01 hydroscopicity. Rosin, therefore, should be used only in the cheaper grades of the vesiculated soap product.

Example 11.Instead. of ushig 10% of trisodium phosphate as in Example 8, use 9% with of rosin soap (sodium ab'ietate etc.) adding the mixture in aqueous solution to neat soap, the proportion of water in .the solution being sumciont on thorough incorporation with the hot neat soap to institute in the latter what would normally be unworkable middle soap, but which, in the prose ice of the rosin saponifled material, and the phosphate compound becomes fluent and sprayable.

Example 12.--A neat soap was made from cocoanut oil 50 parts, tallow parts and hydrogenated fish oil 49 parts, by saponifying in the Example 7. Increasing the trisodium phosusual way with caustic soda. This was incorporated with soda ash 4% and water to make a total water content of 44%. The material was spray-dried by forcing from the supply at lbs. pressure and using an atomizing nozzle 5 supplied with steam at 5 lbs. pressure. The heated air for drying entered the drying chamber or tower at a temperature of 420 F. Good I sized particles large'enough to be visible to the naked eye resulted.

Example 13.A soap product of a 20-80 cocoanut oil-tallow composition was made up to contain 2% common salt and a water content of 44.6%. This was also spray-dried at the same air temperature (420 F.) and at the same'soap 15 pressure. Glassy but slightly opaque particles of the desired good size were obtained, containing soap yielding objectionably large particles, or

ones that would be imperfectly dried. While not limiting myself to any particular degree of pressure or temperature I may spray under a pressure of say, between and 300 pounds with the degummed middle soap at a temperature of about to 200 F., or higher, or lower. The spray drying chamber is supplied with an abundance of preheated air at the temperature appropriate to form the glassy particle of. vesiculated wall structure. may range, preferably, between 350 and 500 F., but higher or lower temperatures may be employed in some cases. Preferably I seek to have so large a volume of heated air in proportion to the amount of the middle soap supplied that the temperature of the exit gases is at, or near, the

boiling point of water; this being with the employment of initial air preheated to within the range of the temperature specified. It should be understood, however, that if lower temperatures are employed chambers of greater dimensions are needed in order to secure a sumciently prolonged exposure of the spray material to drying action.

The heated air may be brought into contact with the spray of the degummed middle soap in any suitable manner, such as with any one of the well known spray dryingsystems. using either concurrent or countercurent flow of the drying air, and the like.

Although the term middle soap is recognized to apply to that phase of soap in which an extremely gummy state obtains, I' consider for the purposes of this invention that the degummed product alsois middle'soap, and have used the terms interchangeably in the foregoing.

In some operations of the drying art it has been customary to spray-dry neat soap under temperature conditions which produce an inflated particle, but the present invention does not ordinarily contemplate pulling or inflating the particle to any substantial extent; although this may be done, if desired, by the regulation and control of temperatures. and other condi 7 tions as the art prescribes for making the infiated particle from kettle soap. I desire especially to obtain a powdered soap in fairly compact form, and the distention of the soap particle by such inflation step adds bulk without a 5 The air temperature 35 corresponding increase in amount of detergent present. I seek; therefore, to produce a bulk product which as a whole is denser, and,'therefore, prefer that the temperature control, and the like, he oi such a character that a nonpuffed, or only slightly pulled particle results.

Thus, I may obtain a product composed substanti'ally of hollow glass-like wall-vesiculated and substantially non-pufled particles of middle soap range carrying a degumming agent. Further it the degummingagent is o! the electrolyte type I may, in some cases, increase the content thereof to a point where actual precipitation of the chemically-hydrated middle soap results, thus forming a slurry or magma.

In this case, however, care should be taken not to introduce a quantity of electrolyte subin excess of thatwhich constitutes wall-saturaot soap, the remainder being largely hydrated soda ash in crystallized i'orm.

In this case I merely I: when desired to 7 provide a proportion of electrolyte only slightly tion.

What I claim is:

-1. The process for making comminuted soap which comprises preparing a soap composition consisting of middle soap together with-a de- 1! gumming agent in sufllcient proportion to reduce the viscosity to a sprayable condition but not sufllcient to cause a separation of crystalline material from the soap, spraying'the same into a chamber heated by a current or heated gas, and collecting the dried soap' as finely divided material composed largely of hollow glasslike; wall-vesiculated, substantially non-pulled particles.

2.Process according .to claim 1 wherein Y a T middle-soap degumming agent is employed in proportion slightly in excess of wall saturation in the final product.

3. Process according toclaim 1 wherein the proportion of degumming agent does notexceed 3 per cent of the material as sprayed.

a CARLETON ELLIS. 

